With the current development of camera modules, module production involves assembling main components such as chips and lenses. The quality of the lens assembly and the cooperation between the lens assembly and the module are the main factors affecting the image quality of the optical system. In the current production, image quality is ascertained by controlling the quality of the lens assembly, tolerances of the main components, and the assembly tolerance of the module. The lens assembly and the module are generally produced by controlling the tolerances of components, namely the assembly precision, and carrying out product testing to ensure the image quality. This method has very high requirements on the components and the assembly process, and the image quality of the product cannot be predicted before testing, which may lead to a great yield loss for high-end products, resulting in high manufacturing costs of the lens assembly or the camera module.
In conventional module design, due to the quality of the lens assembly and assembly of several elements with inclination tolerances, the imaging plane of the lens assembly on the photosensitive chip is inclined relative to the ideal plane. In the case of central focusing, the definition at the periphery of the image decreases with the inclination of the image plane, resulting in uneven imaging definition of the field of view. In addition, due to the tolerance introduced during lens fabrication, field curvature (that is, the central focus and the peripheral focus are not in a same plane) occurs during imaging of the optical system after assembly. In this case, the image quality of the camera module is also affected.
Therefore, how to improve the production efficiency, reduce costs, and improve the image quality in the camera module production, is currently still the important direction for the development of modules. In addition, during the production of the camera module, measures have already been taken to properly adjust the assembly of the camera module, to overcome the defect of decrease in the image quality of the camera module caused by factors such as eccentricity, the image plane inclination, the field curvature, and the peak during the assembly process of the camera module, thereby improving the production efficiency and image quality of the product. Therefore, how to adjust the elements assembled in the optical system quickly by using an optical method during module assembly and production to ensure the image quality and improve the product yield remains currently an urgent problem to be solved in the camera module production.
With the continuous development of various smart devices, higher requirements are imposed on camera modules and various camera devices. As the lens assembly is an indispensable component in the camera module or camera device, higher requirements are also imposed on the lens assembly.
On one hand, the image quality is an important factor for evaluating the quality of the lens assembly. After satisfying basic conditions, the lens assembly design is in constant pursuit to improve the image quality.
On the other hand, another important aspect that needs to be considered in the lens assembly design is how to quickly reach the design standard and widely apply it to practical production to improve the product yield.
In the existing lens designs, a single variable lens is generally used. In other words, in the design process, lenses are independent of each other. In the design process, the impact of each lens on the image quality is evaluated separately, and each lens is separately adjusted, to meet the final design requirements.
For existing design methods, a single lens has great impact on the image quality of the entire lens assembly, and much attention needs to be paid to single lenses. The larger the number of lenses is, the more complex the adjustment will be, making it more difficult to meet the high resolution requirements of the camera module. In the design process, the adjustment of a single lens may have great impact on the image quality of the entire lens assembly, for example, increase the sensitivity of the lens assembly. In contrast, when multiple lenses are used in cooperation, the lenses can compensate for each other, so that a lens assembly with high image quality can be obtained by using lenses whose quality is not high. This aspect is entirely not considered in existing design methods.
Further, the designed lens assembly needs to be used in practical production. In existing design methods, every lens needs to be produced according to design requirements, and during the assembly process, the error introduced during the assembly of each lens will affect the final image quality of the lens assembly. The larger the number of lenses is, the heavier the yield loss of the lens assembly caused by component tolerances and limited assembly precision will be.